Mononuclear and Polynuclear Copper(II) Complexes Derived from Pyridylalkylaminomethylphenol Polypodal Ligands

Abstract

Four mononuclear complexes [Cu(HL(1))Cl]PF(6).CH(3)OH (1), [Cu(HSL(1))Cl]PF(6).0.75H(2)O (2), [Cu(HL(2))Cl]PF(6).CH (3)OH (3), [Cu(HSL(2))Cl]PF(6).1.5CH(3)OH (4), and two polynuclear complexes [Cu (2)(SL(2))(2)](PF(6))(2).2CH(3)OH (5) and {Cu[Cu(SL(2))(Cl)](2)}(PF(6))(2) (6) (HL(1): 2-[(bis(2-pyridylmethyl)-amino)methyl]-4-methylphenol; HSL(1): 2-[(bis(2-pyridylmethyl)amino) methyl]-4-methyl-6-(methyl-thio)phenol; HL(2): 2-[(2-pyridylmethyl)(2'-pyridylethyl)-aminomethyl)]-4-methylphenol; HSL(2): 2-[(2-pyridylmethyl)(2'-pyridylethyl)amino-methyl]-4-methyl-6-(methylthio)phenol were obtained and characterized. The crystal structures of the mononuclear complexes 1-4 show the copper centers in a square-base pyramidal environment with the phenolic oxygen coordinated at the axial position. Dinuclear complex 5 has two copper centers with different geometry and bridged by phenoxo oxygens; one of the copper atoms is square pyramidal while the other can be described with a highly distorted octahedral geometry with a long Cu-S distance (2.867 A). Density functional theory calculations were used to obtain the reported structure of 6, since single crystals suitable for X-ray diffraction were not isolated. Magnetic studies done for 5 and 6 show an antiferromagnetic behavior for 5 (J = -134 cm(-1)) and a ferromagnetic behavior for 6 (J = +11.9 cm(-1)). Redox potentials for the mononuclear complexes were measured by cyclic voltammetry; the values show the effect of the chelating ring size (-213 mV and -142 mV for Cu-HL(1) and Cu-HL(2), respectively) and the presence of the thiomethyl substituent (-213 mV and -184 mV for Cu-HL(1) and Cu-HSL(1), respectively).